Non-Parametric tests, Mann Whitney U, Wilcoxon Signed Ranks T-test

Question 1

What is the Mann-Whitney U test?

Answer 1

The Mann-Whitney U test is a non-parametric test used to compare differences between two independent groups when the data are not normally distributed.

Question 2

When should the Mann-Whitney U test be used?

Answer 2

Use the Mann-Whitney U test when the assumptions of the independent t-test (normality, interval data) are violated.

Question 3

How do you interpret the Mann-Whitney U test results?

Answer 3

A significant p-value (<0.05) indicates a significant difference between the two groups. The U-value represents the test statistic.

Question 4

What is the Wilcoxon Signed-Ranks test?

Answer 4

The Wilcoxon Signed-Ranks test is used to compare two related samples (e.g., pre-test vs post-test) when the assumptions of the paired-samples t-test are violated.

Question 5

When should the Wilcoxon Signed-Ranks test be used?

Answer 5

Use the Wilcoxon Signed-Ranks test when comparing two related samples and the data is ordinal or not normally distributed.

Question 6

How do you interpret Wilcoxon Signed-Ranks test results?

Answer 6

A significant p-value (<0.05) indicates a significant difference between the two related samples.

Question 7

What is a key difference between Mann-Whitney U and Wilcoxon Signed-Ranks tests?

Answer 7

Mann-Whitney U is used for independent groups, while Wilcoxon Signed-Ranks is used for related (paired) samples.